Conventionally, there has been known a KVM (K: keyboard, V: video, M: mouse) switch that switches a plurality of computers when a console composed of a key board, a mouse and a monitor is shared between the plurality of computers (see Japanese Laid-open Patent Publication No. 2005-18135). The KVM switch can be cascade-connected to another KVM switch
FIG. 1 is a system including a plurality of KVM switches cascade-connected to each other, a plurality of computers, and a keyboard and mouse. Here, in FIG. 1, elements relating to video data are omitted.
A system 10 illustrated in FIG. 1 includes computers 1 and 2, a master KVM switch 3, a slave KVM switch 4, and a keyboard and mouse 5. The computer 1 includes a USB port 1a that functions as a USB (Universal Serial Bus) host, and is connected to a USB port 3d of the master KVM switch 3 via a USB cable 6. The computer 2 includes a USB port 2a that functions as a USB (Universal Serial Bus) host, and is connected to a USB port 4d of the slave KVM switch 4 via a USB cable 7.
The master KVM switch 3 includes a USB port 3a that functions as a USB host, a controller 3b controlling the operation of the whole KVM switch 3, a switch 3c switching USB ports 3d to 3g, and the USB ports 3d to 3g that function as USB devices. The slave KVM switch 4 includes a USB port 4a that functions as a USB host, a controller 4b controlling the operation of the whole KVM switch, a switch 4c switching USB ports 4d to 4g, and the USB ports 4d to 4g that function as USB devices. The USB port 4a is connected to the USB port 3g via a USB cable 8. The keyboard and mouse 5 that functions as a USB device is connected to the USB port 3a of the master KVM switch 3 via a USB cable 9.
The keyboard and mouse 5 transmits key codes and mouse data to the master KVM switch 3 or the slave KVM switch 4.